Stockholders' Equity - Common Stock Rollforward (Detail) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Shares of common stock issued
Shares at January 1	516.0	513.0	509.0
Exercise of stock options	1.31	1.00	2.00
Issuance of restricted stock	2	2	2
Shares at December 31	518.6	516.0	513.0
Shares of common stock held in treasury
Shares at January 1	17.6	17.0	16.0
Shares received for restricted stock vested and options exercised		1	1
Shares at December 31	18.1	17.6	17.0
Shares of common stock outstanding at December 31	501	498	496

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- Definition

Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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- Definition

Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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- Definition

For net-share settlement of share-based awards when the employer settles employees' income tax withholding obligations, this element represents the number of shares the employees use to repay the employer.

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- Definition

Number of shares issued during the period related to Restricted Stock Awards, net of any shares forfeited.

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Number of share options (or share units) exercised during the current period.

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- Definition

Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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